Discoloration on ceiling. Mold?

Hi all! Moving into rental house soon and the landlord sent over some pictures of the current condition and these pictures stood out to me. In one of the bedrooms there is some discoloration where the wall meets the ceiling.

Curious what you think it might be and if I should request it's fixed before I move in (in a couple weeks)? To me it looks like mold, likely growing due to a lack of ventilation in that area or something.

But I'm no expert and haven't experienced it before. If anybody has any knowledge that would be great, thanks!

Pic: https://imgur.com/a/N50qzIg